The present industrial requirements for automated machining has generated new, efficient and more effective means to evaluate chip breaking performance. The assessment or predictability of chip form or chip breaking performance is, however, a very difficult task due to inadequate understanding of various interrelated factors, such as, work and tool material properties, chip groove geometry and cutting conditions. In addition, with the continuous advancement of cutting tool technology, a wide variety of new, innovated tool materials and coating techniques have been developed which further complicate the process of predictive assessment. Therefore, no predictive theory has so far been developed to accurately and reliably estimate chip form or chip breaking performance.
Numerous studies and research projects have been undertaken during the last thirty years with hopes of better understanding the nature of chip flow and chip-curl over groove and obstruction type chip-breakers. For example, these studies range from an early work investigating chip curl with obstruction type chip breakers (see Nakayama, K., "Chip Curl in Metal Cutting Process", Bul. of Faculty Engg. Yokohama National University, 1962, Volume 11, p. 1) to later work performed on the actual mechanisms of chip flow, chip curl and chip breaking through high speed filming experiments (see, Jawahir, I. S., "On the Controllability of Chip Breaking Cycles and Modes of Chip Breaking in Metal Machining", Annals of the CIRP, 1990, Volume 39, No. 1, p. 47). Still, despite .continuing efforts in modeling and developing theoretical foundations for chip breaking, very little progress has been made thus far.
The best chip form or chip breakability guides available today are chip charts, available from tool insert vendors, which are based upon feed-depth of cut mapping of producible chips. However, these charts do not fully serve the purpose for which they are developed because variable factors, such as, nose radius, side cutting angle, and cutting speed, all of which drastically alter the chip form or chip breakability patterns, are generally not taken into consideration when producing the chip charts. Routinely, these chip charts are developed from limited experiments on one work material with one nose radius and one side cutting angle at a given cutting speed.
In addition, many tool manufacturers recommend two completely different chip grooves for the same application range. To further compound the problem, no comparative assessment is available among tool inserts which are produced among different manufacturers and are recommended for the same application, although, in practice the tool inserts have been found to behave quite differently. Thus, the present situation is not only due to a lack of fundamental knowledge of chip breaking, but also due to the absence of standards for chip groove classification to identify the most profound geometric parameters of tool inserts and to provide a basis for comparison of chip breaking performance. A need is therefore identified for an improved method for assessing chip breaking performance of a selected tool insert.